Distilling arrangement



Jan. 12; 1965 w. ROSE ETAL 3,1

DISTILLING ARRANGEMET Filed May 17. 1960 3 Sheets-Sheet 1 FIG] mlm-wmq 5Jan. 12, 1965 w. ROSE ETAL DISTILLING ARRANGEMET 3 Sheets-Sheet 3 FiledMay 17. 1960 3 1:. H. HCQDF mcmuc d wr/nvmes United States Patent3,165,455 DISTILLENG ARRANGEMENT Werner Rose, Bochurn, and HerbertKolenda, Essen, Germany, assignors to GEA-Luftkuhler-Gesellschaftm.b.H., Bochum, Germany Filed May 17, 1969, Ser. No. 29,684 Claimspriority, application Germany, May 21, 1959,

Claims. ci. 202 is9 ture which does not condense in the spiraltube-chiefly the inert carrier gas or any other inert gas componentsaredrawn off at the lower end of the spiral tube. The spiral tube istherefore connected to the head of the column in condenser-fashion.

This known column head condenser is open to the objection that, due tothe considerable differences in temperature of the atmosphere, the dropin temperature available for the condensation is subject to strongfluctuations so that the cooling efiiciency of the condenser isdependent to a great extent upon the actual air temperature. Moreover,the cooling effect is also strongly influenced by the strength of theactual air movement so that this air-cooled condenser-regarded as awhole-possesses such a low degree of efficiency that it cannot come intoquestion for use in practice. The great dependency of the cooling effectupon the actual temperature and movement of the atmosphere would lead toa very variable quality and quantity of the product separated by thecondenser and consequently 'to technically and economically prohibitivefluctuations in the operation of the entire rectifying or distillingcolumn. In rectifying or distilling media with a relatively high settingpoint such a condenser would beentircly useless, because it would not bepossible to avoid with certainty dropping below the setting point atwhich these media become viscous or thick so that they can no longerflow downwards under the action of gravity. 7 i

For this reason air-cooled condensers have not been introduced inpractice for the head product of distilling or rectifying columns butcondensers cooled with water or other liquids (for example a mixture of27% diphenyl and 73% diphenyloxide) have been given preference,particularly in large-scale plants, as these enable better degrees ofefflciency to be attained owing to the possibilities of betterregulation. In order to avoid too strong under-cooling of the condensingmediumwhich is particularly important in the case of easily settingmediait is, however, frequently necessary in the case of watercooledcondensers to preheat the cooling liquid so as to avoid uneconomical andinadmissible undercooling of the condensate. Another objection to theseliquid-cooled condensers is that even slight leakages in the coolingtube cause a pollution of the product so that the cooling liquidforexample water-under high pressure mixes with the condensed product andpossibly reacts chemically therewith with the result that the productbecomes useless. To exclude this danger, extensive safety measures aregenerally necessary which consist for example in erecting theliquid-cooled condenser adjacent the column. As, however, such arectifying column only operates when a portion of the productprecipitated in the con- "ice 'denser flows back over the exchangeplates or trays of the rectifier column, such an arrangement requirespumps which feed back a portion of the condensate through special returnconduits onto the uppermost exchange plate or tray. With the usualheight of such rectifier columns, which often amounts to 30 to 50meters, extensive additional arrangements are necessary which result inan increase of the initial and working costs of the plant. Moreover thevaporous product passing out from the head of the column must in thiscase be deflected several times if necessary which, particularly in thecase of plants operating under high vacuum, leads to serious flow lossesdue to the high flow velocities required by the large specific volumesof the vapor.

In spite of these disadvantages connected with the use of liquid-cooledcondensers for the product from rectifying and distilling columns, thesehave hitherto been accepted because with air-cooled condensers operationmeeting the economic and technical requirements could not be attained.

It is the object of the invention to overcome these disadvantages whichhitherto obstructed the use of aircooled condensers and condensersconnected up in condenser-like fashion for the head product ofdistilling or rectifying columns.

The invention provides a distilling arrangement including an air-cooledcondenser for the head product of a distlling or rectifying column withcondenser tubes connected to the column head, the condenser comprisingat least one jacket composed of condenser elements with upright ribbedtubes surrounding the head with lateral clearance and forming inhorizontal section an equilateral polygon, and at least one propellerblower arranged above the column head in the projection of the polygonfor producing a current of cooling air brushing against the condenserelements and regulatable in strength and if necessary in direction.

By this means it is possible, while providing a compact and space-savingdistilling arrangement and without appreciably increasing theconstructional height of the column, to accommodate in the region of thehead of the column an air-cooled condenser with high cooling capacity,the operation of which can also be regulated, in the event ofatmospheric temperatures fluctuating considerably, so that a constantquality of the head product is always ensured.

The polygonal arrangement of the condenser elements surrounding the headof the column firstly offers the advantage that the upper part of thecolumn can be used as carrier structure for the condenser elements sothat foundations and staging, particularly adjacent the column, are notrequired for supporting the condenser. In

addition, by this arrangement long conduits for the vapors to becondensed and for deflecting these, are avoided with the result thatflow losses caused thereby are eliminated.

By regulation of the strength and/or the direction of the stream ofcooling air, which can be effected for example by throttling ordeflecting devices, a regulation of the number of rotations or reversingthe direction of the propeller blower, or by adjusting the propellerblades, the cooling capacity of the condenser can be adapted to j thetemperature of condensation of the actual head product so that anyundesirable or impermissible under-cooling of the condensate, forexample dropping below the setting point or the freezing pointtemperature in the case of solidifying media, is reliably avoided. Inthis manner even large fluctuations inthe atmospheric temperature orwind velocity can be easily compensated without affecting the quality ofthe head product of the column.

In the case of slight fluctuations in temperature which 7 are to beexpected and when working media which do not congeal, it is as a rulesufficientif the cooling air current brushing over the condenserelements is merely adjustable in strength yet retains its directionpermanently. Moreover an arrangement of this kind is so designed thatthe propeller blower or blowers socks or suck the cooling air throughthe condenser elements or the space left between the condenser elementsand the head of the column and blows or blow it upwards into theatmosphere.

In'cases when particularly low external temperatures are to be expectedas well as when distilling for rectifying easily congealable media, itis on the other hand more advisable to. provide also possibilities ofreversing the direction 'of flow of the cooling air current so as toeffect, in the case of particularly low external temperatures, apreheating of the cooling air on the outer wall of the head of thecolumn before this air brushes against the outer side of the ribbedtubes of thecondenser elements. Another possibility, in the case 'ofmedia with a relatively high congealing point, of reliably excluding anyinadmissible undercooling of the condensate, consistsin that anarrangement is provided which enables the condenser to be switched"overpartly or entirely to boiling components of the head product takesplace in the region of the height of the condenser elements, whichresults in relieving the condensers and enables the production of a verypure condensate.

Another advantage of the condenser proposed according to the inventionconsists in that the arrangement of the condenser elements in the formof one or more jackets surrounding the column head enables largeheat-extogether with the inert carrier gas or any other inert componentsof the gas. In addition, in the case of an aircooled condenser, thepumping ofthecooling medium on the column head, which is necessary inthe caseof a liquid cooler arranged in the region of the column head, aswell as thepurnps and conduits required therefor, are dispensed with,which results in a considerable reduction in the initial and runningcosts of the plant. Finally, in the case of an air-cooledcondenser, nomeasures are necessaryto protect the cooling medium against the dangerof freezing in the event of extremely low I atmospherictemperatures, asi'n'thecase of liquid coolers.

, ticularly low atmospheric temperatures is prevented by e the hot aircurtain produced by the column.

changing surfaces to be accommodated in a very small space so that itpresents no dilficulties to completely condense the large quantities ofvapor produced in recti fying or distilling columns with high throughputcapacity. 7

The arrangement of the condenser elements in the region of the columnhead also has an advantageous effect in that, in addition to the coolingair current produced by the propeller blower or blowers, the natural airmove ment in the region of the column head is also utilized for coolingthe condenser tubes.

The number of sides of the polygon formed by the condenser elements canVary and is dependent upon the number of condenser elements actuallyrequired, that is the necessary cooling output of the condensers. Thus,

'forexample, "in the case of larger cooling outputs, the

condenser elements can form in cross-section a prefer ably equilateraloctagon or decagon, whereas in the'case of lower outputs or severalcondenser jackets arranged one within the other, polygons with a smallernumber of sides are preferable. also produces a very stable constructionin itself which,

due to its advantageous adaptations to the cross-sectional.

shape of the column. head, enables 'it to be connected The polygonalcircular shape.

to the column head by means of relatively simple and light structuralelements in such a manner that it is I capable of withstanding thestrongest stresses, such as trating through leaky points would bedirectly sucked off Regarded as a whole,the condenser proposed accordingto the .inventionis, as compared to the previously known constructions,characterized by the possibility of much better regulationand aconsiderably higher-degree of efiiciency, while the initial andrunningcosts of the plant are far lower and the reliability of operation is 1much greater.

In a preferred form of the distilling'a'rrangement, the condenserelements of each jacket are similar to each other and arranged insubstantially vertical, planes, Thus a uniform distribution of theheat-exchangingsurfaces over-"the peripheryof the column head isattained so that, independently of the actual direction of the. wind,the natural air movement can be utilized to a uniform extent foradditionally cooling the condenser tubes. By the arrangement of thecondenser elements in substantially vertical planes, a betterutilization of the total cross-section of the ribbed tubes for thecondensatioriprocess is attained, as compared with aninclinedarrangement. Moreover, such vertical arrangementof the condenserelements adapts itself better to the column head which is mostly ofcylindrical construction: r

As a rule it is advisable to connect the upper end chambers of thecondenser elements to a common circular conduit constructed as adistribution conduit and which is connected'with the head of the columnby means of several connection pieces distributed at substantiallyuniform distances apart around the peripery. thereof. The concondenser'element'sonone half of the'periphery of the column head beingsubjected to a particularly intensive natural impingement of air.

A particularly simple construction is produced by fixing the condenserelements to the upper annular conduit in suspended arrangement, theconnection pieces being constructed as carrier elementsfor the upperannular conduit and condenser elements fixed thereon.

The lower end chambers of the condenser elements are preferably alsoconnected up to a common annular conduit which in turn is connected to asuction device and can beselectively connected up witha return conduitleading to the column head and a discharge conduit for the finishedproduct. s

In cases where it is a question of obtaining particularly largethroughput outputs, it is advisable to provide two or more radiallyspaced condenser jackets'surrounding each other as well as the head ofthe column, which jackets form in horizontal section geometricallysimilar polygons. Between the'condenser jackets surrounding each 'otherdevices for moistening the cooling air'are preferablyprovided inorder toreduce the temperature of the cooling.

air to its moisture temperature after it has flowed through the firstcondenser jacket. By this means the cooling air admitted to the nextfollowing condenser jacket has about the same temperature as the airsucked out of the atmosphere and flowing through the first condenserjacket. The air moistening device preferably consist of spraying nozzlesdistributed at substantially uniform distances apart over thecross-section of the current of cooling air in opposite direction to theflow of air.

Whereas the lower end chambers of the condenser elements arehermetically joined to the outer wall of the head of the column by ashell, it isadvisable to connect the upper end chambers of the condenserelements to a second shell covering the end face of the head of thecolumn with clearance and provided with apertures for the arrangement ofpropeller blowers. A particularly advantageous form of construction isobtained by constructing the upper shell as a prismatic hood, the airapertures provided in the upper substantially horizontal end face ofwhich are lined with casings serving as intake passage, blower housingor diffuser. In order to enable the strength and/ or direction of thecooling air current to be changed in the desired manner, propellerblowers which are variable in speed and/or reversible in direction ofrotation are provided. Instead of using several propeller blowersdistributed over the end face of the upper shell which is advisable inmany instancesonly a single propeller blower may be arranged coaxiallyto the head of the column, the speed of which blower is regulatablepreferably infinitely.

A preferred embodiment of the invention will now be described by way ofexample and with reference to th accompanying drawings, in which:

FIG. 1 is a side elevational view of a distilling arrangement embodyingthe invention;

FIG. 2 is a section taken on line IIII of FIG. 1;

FIG. 3 is a top plan view, on a reduced scale, of FIG. 2, and

FIG. 4 is a section, on a reduced scale, taken on line IV-IV of FIG. 2.

FIGS. 1 and 2 show a distilling arrangement including a rectifyingcolumn having a head 1 which may have a diameter of, for example, 3 to 5meters and a height of, for example, 20 to 50 meters. Exchange plates ortrays 2, only one of which is shown in FIG. 4, are arranged one abovethe other inside the column and constructed in a known manner.

Above the uppermost exchange plate or tray, not shown in the drawings,the head 1 of the column is provided with several laterally projectingconnection pieces 3 preferably arranged at uniform distances apartaround the periphery thereof, which connection pieces are equipped withregulating and shut-off elements 4 which can be operated independentlyof each other. The connection pieces 3 carry an upper annular conduit 5constructed as a distribution conduit, which, in plan view (FIG. 3)forms an equilateral polygon, namely an equilateral polygon, namely anequilateral hexagon. The upper end chambers 7 of condenser elements 8and 8a are connected up to the annular conduit 5 by a number of branchconnection pieces 6 corresponding to the number of sides of the polygon,which condenser elements form two condenser jackets encircling the headof the column with different clearances. The condenser jackets, like theupper annual conduit 5, are in the shape of an equilateral polygonwhichin the example illustrated in the drawings is an equilateral hexagonandarranged in relation to each other in similar geometrical fashion andcoaxially to the longitudinal axis of the column head 1. The distancebetween the inner and outer condenser jackets is about three times asgreat as the distance between the inner condenser jacket and theperiphery of the column head 1.

Lower end chambers 9 of the condenser elements 8 and 8a are connected toa common lower annular conduit 11 by means of connection conduits ofconsiderably smaller cross-section than the connection pieces 6, saidlower annular conduit 11 being connected up with an exhausting devicefor the inert carrier gas and other inert components of the gas, whichdevice is not shown in the drawings, and can also be selectivelyconnected up with a return conduit leading to the column head 1 and adischarge conduit for the finished product, which conduit is likewisenot shown in the drawings.

The connection pieces 3 for the upper annular conduit 5 are at the sametime constructed as carrier elements so that the condenser elements 8and 8a fixed in suspended arrangement on the upper annular conduit 5 arecarried by the connection pieces 3.

Below the lower end chambers 9 and the lower annular conduit 11 asubstantially horizontal platform 12 is provided the inner edge of whichextending up to the periphery of the column head 1 is mounted inbrackets 13. The platform 12 is also held in position by inclined struts14 which are fixed in brackets 15 provided on the column head 1. Theplatform 12, in the example illustrated in the drawings, is in plan viewpolygonal corresponding to the arrangement of the condenser elements 8and 8a and projects on all sides beyond the periphery of the outercondenser jacket formed by the condenser elements 8. In this outer zonethe platform 12 is constructed as a Working platform and provided with aguard railing 16.

In the form of construction illustrated in the drawings, the condenserelements 8 and 8a are, in addition to being suspended on the upperannular conduit 5, supported by substantially T-shaped supports 17resting on the platform 12.

The platform 12 also carries a prismatic sheet-metal shell 18corresponding with the inner condenser jacket as regards shape anddimensions and having the form of an equilateral polygon incross-section like the condenser jacket, as can be seen from FIG. 3. Thepolygonal shell 18 is provided in the region of the condenser elements8a of the inner condenser jacket with apertures of a size correspondingwith the surface area of these elements, which apertures are covered bythe condenser element-s 8a arranged in front of them. The upper end ofthis polygonal sheet-metal shell 18 is closed by a substantiallyhorizontal sheet-metal end plate 19, which, in the example illustratedin the drawings, is provided with four symmetrically arranged apertures20 for accommodating propeller blowers 21. The upper part of the shell18 and the plate 19 thus form a prismatic hood enclosing the end face 1aof the column head 1 with clearance. The end plate 19 of this shell is,as can be seen from FIG. 2, supported against the end face 111 of thecolumn head by a prop 22 arranged coaxially to the longitudinal axis ofthe column head 1.

The apertures 20 in the upper end plate 19 of the condenser shell arelined with casings 23 which serve as blower housings and also form shortsuction passages or diifusors.

The propeller blowers 21 are driven in constant direction by variablespeed motors 24 so that they suck cooling air through the double jacketof the condenser elements 8 and 8a in the direction x into the spacebetween the inner condenser jacket and the periphery of the column head1 and blow it upwards into the atmosphere in the direction 2: Thepropeller blowers 21 are arranged in the outer region of the upper endplate 19 of the condenser shell so that they ensure a uniform brushingof the cooling air over all condenser elements 8 and 8a distributedaround the periphery of the column head 1, with a relatively low loss offlow. As the shell composed of the end plate 19 and the polygonal wall18 is completely closed except for the appertures for accommodating thecondenser elements 8a and the propeller blowers 21, and also theplatform 12, at least in the region located within the polygonal wall18, is of closed construction and hemetically connected to the externalperiphery of the only through the condenser elements 8 and 2a Thecondenser elements 8 and 8a consist in a known manner of end chambersland 9 connected-'by a relatively large number of ribbed tubes arrangedparallel to one another and at a distance apart. In the form ofconstruction illustrated in the drawings, the condenser elements 8 andSa have only a single row of ribbed tubes in the direction of flow x ofthe cooling air. However, condenser elements with two or possibly morerows of tubes arranged 'one behind the other in the direction of flow atof the cooling'air might also be used.

. Between the inner and outer jackets formed by the condenser elements 8and 8a thereis'an air moistening device, as can be seen'from FIGS. 2 and.4. This air moistening device consists of a plurality of sprayingnozzles 25 arranged at uniformdistances apart and-distributed over thecross-sectional area of the cooling air stream.

These spraying nozzles 25 point in theopposite direction to the flow xof the cooling air current and cause a reduction of the cooling airtemperature to its moist temperature between the inner and outercondenser jackets. Spraying liquid, preferably water, is fed throughfeed conduits provided with regulating devices, not shown in thedrawings.

The end plate 19 ofthe condenser shell is also constructed as aworkingplattorm like the outer portion of the platform 12 and for thispurpose is provided with a guard rail or railing 26.

- Instead of four propeller blowers 21 arranged substantiallysymmetrically to the longitudinal axis of the column head 1, a larger orsmaller number of propeller blowers may be provided when necessary. Inthe case where only one propeller blower with a suitably large output isprovided, the space between the upper end plate 19 of the shell and theend face In of the column head 1 must be made correspondingly large. Inthis case the blower may be driven through the intermediary ofa-suitable gearing by a variable speed motor arranged for example on theend face 1a of the column head.

The vapors collecting above the uppermost exchange plateor tray of thecolumn head 1 are fed through the connection pieces 3, the upper annularconduit 5, the branch connection pieces 6 and the upper end chambers 7to the condenser elements 8 where they are condensed by the air brushingagainst the outer side of the condenser tubes. The condensate flowsthrough the lower end chambers 9 and the connection conduits 10 and 10ainto the lower annular conduit 11 whence it is either returned into thecolumn head 1 or drawn off as finished product. Hereby it is possible towork both under vacuum and also under pressures exceeding atmosphericpressure.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description and all changeswhich come within the meaning and range of equivalency of the claims aretherefore intended to be embraced therein.

We claim: I I

l. A distilling arrangement comprising, in combination, an elongateddistilling column having an upper end portion in which the vaporizedhead product collects; air cooled condenser means comprising at leastone jacket composed of aplurality of groups of finned tubular condenserelements spaced from each other and surrounding said upper end portionof said column spaced therefrom and having each an upper end located ata higher elevation than the lower end thereof and a length which is onlya small fraction of that of said column; means connected to the upperends of a plurality of said condenser elements and to the upper end ofsaid column for carrying said condenser elements on said upper end.of'said column and for connecting the" interior of said upper end ofsaid column in parallel with the interior of said condenser elements sothat the vaporized head product may pass through saidscondenser elementsto condense therein, whereby the condensate will flow in downwarddirection through said element s; means connecting thelowenen-ds'offsaid'condenser elements in parallel to each other; and aircirculating means located in the region of saidupper end portion of saidcolumn and within the area between said column and said jacket forcirculating air between said condenser' elements and through the spacebetween the latter and said upper end portion ofsaid column. V t

2 A distilling arrangement as set forth-in claim 1 in which saidcondenser'ele'ments are arranged substan tially verticalJ I. a t 3.Adistilling arrangement comprising, in combination, an elongateddistiliing column having ahead at its upper and in which the vaporizedhead product collec'ts; air cooled condenser means comprising at leastonejaclret composed of a plurality of groups of finned tubular,substantially vertically extending condenser elements, spaced from eachother and surrounding said head of said column spaced therefrom and eachhaving a length which is'only a small. fraction of that of said column;means connected to the upper ends of said condenser elements and tothe'head of the columnfor carrying said condenser elements on said headand forconnecting the'interior ofsaid head in' parallel with theinterior of said condenser elements so that the vaporized head, productmay pass throu-gh said' condenser elements to condense therein, wherebythe condensate. will flow in downward direction through said elements,-said means comprising an annular distributor'conduit disposed above andcommunicating with the upper ends of said condenser elementsand aplurality ofsuostantially uniformly distributed connecting piecesconnecting said distributor conduit with saidhead; meansconnecting thelower ends of said condenser elements in parallel to each other; and aircirculating means located above said head and within the cross-sectionalarea defined by saidjacket for circulating air between said condenserelements and through the space between the latter and said head.

4. A distilling arrangement comprising, in combination, an elongateddistilling column having a head atits upper end in which the vaporizedhead pro-duct collects; a shell structure surrounding said head of saidcolumn and having a top wall, an-annular bottom wall engaging said head.and closingsaid shell at its lower end, and a plurality of side wallsextending between 'said top and;

bottorn -walls spaced'fro m said head and each formed with anaperture;air cooled condenser meansgcomprising a plurality of groups of finnedtubular condenser-elements each having an upper end and a lower end andarranged ad acent to and outside of said apertures and forming togethera jacket surrounding said head spaced therefrom and also surroundingsaid shell structure, each of said condenser elements having a lengthwhich is. onlyv a small fraction o'f-that of said columng'meansconnected to the upper ends of said condenser elements and to said headfor carrymgsaid condenser'elements on said head and for connecting theinterior of said head in parallel with the interior of said condenserelements so that the vaporized head product may pass through saidcondenser elements to condense therein, whereby the condensate willflow-in downward direction through said elements; means connecting .thelower ends of said condenser elements in parallel 'to each other andhaving. at least one common delivery end for the condensate; andat leastone blower mounted in an opening formed insaid top wall of said shellstructure for circulating cooling air through said apertures so asto'force that cooling airto flow about said condenser elementsand'tlirough the space between the latter and said head. 7 r r 5. Anarrangement as set forth in claim 1, wherein said jacket forms inhorizontal section an equilateral polygon and said air circulating meanscomprises at least one blower disposed above said upper end portion ofsaid column head.

6. An arrangement as set forth in claim 5, wherein said blower isreversible.

7. A distilling arrangement as set forth in claim 1, wherein saidcondenser means comprises a plurality of concentric jackets spaced fromeach other and forming in horizontal section geometrically similarpolygons.

8. A distilling arrangement as set forth in claim 7, further comprisingmeans disposed between said jackets for moistening the cooling air.

9. A distilling arrangement as set forth in claim 8, wherein saidmoistening means comprises spray nozzles which are regularly distributedbetween the jackets for discharging a liquid in a direction counter tothe flow of cooling air.

10. An arrangement as set forth in claim 3, further comprising valvemeans in said connection pieces for regulating the flow of head producttheret hrough.

References Cited in the file of this patent UNITED STATES PATENTS HawkesJ an. 8, Wittemann Feb. 26, Bleicken Dec. 27, Keath Mar. 29, Pugh June16, Hines Feb. 23, Kessel Oct. 25, McGovern June 25, Larrecq June 18,Hunter Sept. 21, Morse Apr. 23, Stanley Mar. 4, Rollins et al Apr. 1,Stutz June 16, Buehler Nov. 10, Sweeney et a1 June 19,

FOREIGN PATENTS Sweden Nov. 1, Austria Apr. 15,

1. A DISTILLING ARRANGEMENT COMPRISING, IN COMBINATION, AN ELONGATEDDISTILLING COLUMN HAVING AN UPPER END PORTION IN WHICH THE VAPORIZEDHEAD PRODUCT COLLECTS; AIR COOLED CONDENSER MEANS COMPRISING AT LEASTONE JACKET COMPOSED OF A PLURALITY OF GROUPS OF FINNED TUBULAR CONDENSERELEMENTS SPACED FROM EACH OTHER AND SURROUNDING SAID UPPER END PORTIONOF SAID COLUMN SPACED THEREFROM AND HAVING EACH AN UPPER END LOCATED ATA HIGHER ELEVATION THAN THE LOWER END THEREOF AND A LENGTH WHICH IS ONLYA SMALL FRACTION OF THAT OF SAID COLUMN; MEANS CONNECTED TO THE UPPERENDS OF A PLURALITY OF SAID CONDENSER ELEMENTS AND TO THE UPPER END OFSAID COLUMN FOR CARRYING SAID CONDENSER ELEMENTS ON SAID UPPER END OFSAID COLUMN AND FOR CONNECTING THE INTERIOR OF SAID UPPER END OF SAIDCOLUMN IN PARALLEL WITH THE INTERIOR OF SAID CONDENSER ELEMENTS SO THATTHE VAPORIZED HEAD PRODUCT MAY PASS THROUGH SAID CONDENSER ELEMENTS TOCONDENSE THEREIN, WHEREBY THE CONDENSATE WILL FLOW IN DOWNWARD DIRECTIONTHROUGH SAID ELEMENTS; MEANS CONNECTING THE LOWER ENDS OF SAID CONDENSERELEMENTS IN PARALLEL TO EACH OTHER; AND AIR CIRCULATING MEANS LOCATED INTHE REGION OF SAID UPPER END PORTION OF SAID COLUMN AND WITHIN THE AREABETWEEN SAID COLUMN AND SAID JACKET FOR CIRCULATING AIR BETWEEN SAIDCONDENSER ELEMENTS AND THROUGHT THE SPACE BETWEEN THE LATTER AND SAIDUPPER END PORTION OF SAID COLUMN.